Meriwether Lewis and William Clark are best known for their expedition from the Mississippi River to the West Coast and back. The expedition, called the Corps of Discovery, was President Thomas Jefferson's visionary project to explore the American West. It began in May of 1804 and ended in September 1806. Before the expedition, Lewis was Jefferson's private presidential secretary. He also served in the military, where he met Clark. After the expedition, Lewis served a short term as Governor of the Territory of Upper Louisiana before he died. Clark lived for many years and held various government positions, including Superintendent of Indian Affairs and Governor of the Missouri Territory.